People crowd on an islet to watch first rush of water through Gamboa dyke, Panama Canal, circa 1910-1914. (Detroit Publishing Co. Photograph Collection/Courtesy Library of Congress/Gift of State Historical Society of Colorado)

1904: The United States agrees to complete the Panama Canal. In both human and financial terms, the canal project is one of the costliest engineering undertakings in history.

The idea of constructing a canal through the Isthmus of Panama had been around for centuries: The first known working plan for a canal was drawn up in 1529 for Spain’s Charles V. But the Europeans, continually warring or intriguing throughout the intervening years, never quite got around to connecting the world’s two greatest oceans.

Serious construction of the Panama Canal was finally begun in 1882 by the French, who, for financial reasons, were forced to abandon the project in 1899. When the Americans took over, the first thing they did was to improve the living and working conditions for the construction crews, who had suffered greatly from mosquito-borne disease under the French.

The first steam shovel resumed excavation at the Culebra Cut on Nov. 11, 1904. It would be almost 10 years before the first ship — the SS Ancon — passed through the locks Aug. 15, 1914.

The 51-mile Panama Canal is a series of locks and dams that raise and lower ships as they pass from Limon Bay in the Atlantic to the Bay of Panama in the Pacific.

Although the canal remains an incredible engineering achievement, its builders failed to anticipate the future of shipping. The biggest problem facing the canal today is its inadequacy in accommodating the large superships that ply the world’s oceans. Because of that, construction of a second Pacific-to-Atlantic canal is being contemplated.